Heat exchanger having header tanks

ABSTRACT

A heat exchanger includes a pair of header tanks and a plurality of tubes. Each of the header tanks includes an outer member and an inner member, The outer member has insertion holes allowing insertion of the tubes, while the inner member has insertion grooves allowing insertion of respective ends of the tubes. The heat exchanger is provided by brazing the so-inserted tubes to the peripheries of the insertion holes of the outer member. In order to suppress capillary phenomenon of a molten brazing filler metal in a clearance between each insertion groove and the tube, a broad portion is formed in the insertion groove to have an inside width larger than an inside width of the insertion hole. When brazing the tube to the outer member and the inner member, the molten brazing filler metal does not reach the tip surface of the tube but remains in the broad portion while maintaining the brazing strength of the tube.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat exchanger having a pair ofheader tanks and a plurality of tubes inserted into the header tanks.More particularly, the invention relates to an attachment structure ofthe heat exchanger where the tubes are brazed to the header tanks.

2. Description of the Related Art

In a heat exchanger, generally, a plurality of juxtaposed tubes arecommunicated with a pair of header tanks opposing to each other at aninterval. Further, heat radiation fins are interposed between theadjoining tubes. In operation, heat exchange fluid flows from one headertank to the other header tank through the tubes. During this flowing ofthe heat exchange fluid, the beat exchanger carries out heat exchangingoperation between the heat exchange fluid in the tubes and another heatexchange fluid passing through the fins.

Meanwhile, when carbon dioxide gas as one supercritical fluid is usedfor the heat exchange fluid for refrigerating cycle and heat pump cycle,it is necessary to assure a sufficient flame-proof strength for theheader tanks due to an increased interior pressure in the beatexchanger. For this purpose, Japanese Patent Application Laid-open No.11-351783 discloses a heat exchanger equipped with header tanks in whicha plurality of cylindrical portions having substantially circularsections are juxtaposed in order to avoid concentration of stress due tohigh pressures, providing a multi-bore structure. In this view, theheader tanks are is formed by extrusions, pressed goods, etc.

In the heat exchanger, each of the header tanks is provided by weldingan inner member to an outer member by caulking. The outer member isprovided with a plurality of insertion holes for the tubes, Inassembling, the tubes are inserted into the inner member through theinsertion holes of the outer member and successively, the tubes arebrazed to the outer member for integration.

In the above-mentioned heat exchanger, if the inner member of the headertank has a plurality of insertion grooves formed therein at positionscorresponding to the insertion holes of the outer member, then itbecomes possible to engage respective ends of the tubes inserted intothe insertion holes of the outer member with the insertion grooves ofthe inner member, thereby effecting both positioning and fixing of thetubes.

In connection, if each of the insertion grooves is formed so as to makeits inside width equal to an inside width of the insertion groove, thereis a possibility that when brazing the tubes to the header tanks, amolten brazing filler metal enters a clearance between the insertiongroove of the inner member and the tube through a clearance between theinsertion hole of the outer member and the tube. Consequently, due tothe capillary phenomenon of the former clearance, the molten brazingfiller metal further creeps in the back of the insertion groove andreaches the tip surface of the tube, so that an opening (communicationpart) at the tip of the tube may be clogged up with the molten brazingfiller metal disadvantageously.

SUMMARY OF THE INVENTION

In the above-mentioned situation, it is an object of the presentinvention to provide a heat exchanger that can prevent the moltenbrazing filler metal from reaching the tip surfaces of the tubes ininsertion into the insertion grooves of the inner member while assuringthe brazing strength about the tubes.

To attain the above object, the first aspect of the invention provides aheat exchanger comprising, a pair of header tanks arranged at apredetermined interval, each of the header tanks including an innermember having at least one insertion groove formed therein and an outermember having at least one insertion hole formed therein and coveringthe inner member thereby defining a hollow part in the header tank, anda plurality of tubes arranged between the header tanks in communicationwith the header tanks, each of the tubes having an end to be insertedinto the insertion hole of the outer member of the header tank and alsoinserted into the insertion groove of the inner member of the headertank, wherein the insertion groove has a broad portion of which insidewidth is larger than an inside width of the insertion hole, wherein thetube is brazed to the outer member's part about the insertion hole.

In the heat exchanger of the first aspect, owing to the formation of thebroad portion of each insertion groove, it is possible to suppresscapillary phenomenon of a molten brazing filler metal in a clearancebetween the inside member and the tube. Therefore, when brazing the tubeto the periphery of the insertion hole of the outer member, the moltenbrazing filler metal does not reach the tip surface of the tube butremains in the broad portion, whereby it is possible to prevent anopening (or communication space) at the tip of the tube from beingclogged with the brazing filler metal.

In a preferred embodiment, the broad portion may be formed over theinsertion groove. In this case, owing to the above formation of thebroad portion, it becomes possible to suppress capillary phenomenon ofthe molten brazing filler metal in the clearance between the insidemember and the tube.

The broad portion may be formed at the bottom of the insertion groove.Then, owing to the broad portion, it is possible to fix the end portionof the tube with both of the insertion hole and an inlet portion of theinsertion groove through the brazing filler metal. As a result, thejoint strength of the tube with the inner member can be enhanced.

The insertion groove is provided, at a bottom surface thereof, with aclearance forming mechanism configured to form a clearance between a tipsurface of the tube and the bottom surface of the insertion groove.

Then, by the clearance forming mechanism, it is possible to prevent anopening at the tip of the tube from being blocked up by the bottomsurface of the insertion groove.

The clearance forming mechanism comprises the bottom surface of theinsertion groove, which is inclined to the tip surface of the tube.

Similarly, it is possible to prevent an opening at the tip of the tubefrom being blocked up by the bottom surface of the insertion groove.Additionally, it is also possible to braze the tube to the header tankwhile making the tip surface of the tube abut on the bottom surface ofthe insertion groove, whereby the assembling workability can beimproved.

The bottom surface inclined to the tip surface of the tube includes anarc-shaped section. Then, it is possible to prevent an opening at thetip of the tube from being blocked up by the bottom surface of theinsertion groove. Additionally, it is also possible to braze the tube tothe header tank while making the tip surface of the tube abut on thearc-shaped bottom surface of the insertion groove, whereby the tube canbe assembled stably.

The clearance forming mechanism comprises a recess formed on the bottomsurface of the insertion groove, at a position opposing the tip surfaceof the tube.

Owing to the formation of the recess on the bottom face of the insertiongroove, it is possible to prevent an opening at the tip of the tube frombeing blocked up by the bottom surface of the insertion groove.

These and other objects and features of the present invention willbecome more fully apparent from the following description and appendedclaims taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a heat exchanger in accordance with thefirst embodiment of the present invention;

FIG. 2 is an enlarged cross-sectional view of a header tank, taken alonga line 2-2 of FIG. 1;

FIG. 3 is an enlarged longitudinal sectional view of the header tank,taken along a line 3-3 of FIG. 1;

FIG. 4 is an enlarged cross-sectional view of a substantial part of theheader tank in accordance with the second embodiment of the presentinvention;

FIG. 5 is an enlarged longitudinal sectional view of the substantialpart of the header tank in accordance with the second embodiment of thepresent invention;

FIG. 6 is an enlarged longitudinal sectional view of the substantialpart of the header tank in the first modification of the secondembodiment of the present invention;

FIG. 7 is an enlarged longitudinal sectional view of the substantialpart of the header tank in accordance with the third embodiment of thepresent invention;

FIG. 8 is an enlarged longitudinal sectional view of the substantialpart of the header tank in the first modification of the thirdembodiment of the present invention;

FIG. 9 is an enlarged longitudinal sectional view of the substantialpart of the header tank in the second modification of the thirdembodiment of the present invention; and

FIG. 10 is an enlarged longitudinal sectional view of the substantialpart of the header tank in the third modification of the thirdembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to accompanying drawings, embodiments of the present inventionwill be described below.

1^(st). Embodiment

According to this embodiment, as shown in FIG. 1, the heat exchanger 1generally includes a pair of hollow header tanks 2, 2, a plurality offlat tubes 3 paralleled with each other to straddle between the headertanks 2, 2 in communication with the header tanks 2, 2 and a pluralityof fins 4 each disposed between the adjoining flat tubes 3 besides theoutermost tubes 4. In the heat exchanger 1, a heat exchange fluid suchas cooling water, flows from one header tank 2 to the other header tank2 through the intermediary of the tubes 3. During this flowing, the heatexchange is carried out between the above heat exchange fluid andanother heat exchange fluid, for example, airflow passing through thefins 4.

As shown in FIG. 2, the header tank 2 includes a U-shaped plate 10 as anouter member and a block 11 as an inner member. The plate 10 is providedby folding an aluminum clad material in a U-shaped manner by pressworking. On the other hand, the block 11 is provided by extruding analuminum material. In assembling, the block 11 is first fitted to theinterior side of the U-shaped plate 10 and successively, respectivecrimp portions 10 a of the plate 10, which are in the form of comb teethprojecting on both sides of the plate 10, are crimped to both outersides of the block 11, providing the header tank 2 in one body.

The block 11 is provided, on its inner side close to the tubes 3 (lowerside of FIG. 2), with a boundary wall 11 a. A pair of groove parts 11 b,11 b having substantial semicircular sections are defined on both sidesof the boundary wall 11 a. The insides of the groove parts 11 b, 11 bare covered by the plate 10 to form a pair of airtight cylindricalportions 12, 12. Owing to the provision of the cylindrical portions 12,12, the header tank 10 is provided with a multi-hole structure.

Of course, both ends of the header tank 10 are closed up by caps 13, asshown in FIG. 1.

The plate 10 has insertion holes 14 formed to allow the tubes 3 to beinserted thereinto, as shown in FIG. 2. Further, the block 11 hasinsertion grooves 15 each formed with a predetermined depth D in theboundary wall 11 a to engage with respective ends 3 a of the tubes 3,respectively. While the ends 3 a of the tubes 3 inserted into theinsertion holes 14 are engaged with the insertion grooves 15, the tubes3 are brazed to the peripheries of the insertion holes 14, ensuring theliquid-tight performance of the header talk 2.

In such an assembling state between the tubes 3 and the header tank 2,an appropriate clearance δ1 is defined between a tip surface 3 b of eachtube 3 and a bottom surface 15 a of each insertion groove 15 toaccomplish communication between the cylindrical portions 12, 12 on bothsides of the boundary wall 11 a.

According to the first embodiment of the invention, as shown in FIG. 3,each insertion groove 15 is provided with a broad portion 16 whoseinside width W2 is larger than an inside width W1 of the insertion hole14 in the plate 10 in order to suppress the capillary phenomenon ofmolten brazing filler metal R in respective clearances δ2 each betweenthe tube 3 and the inner wall of the insertion groove 15.

Additionally, it is noted that the broad portion 16 is formed throughoutthe insertion groove 15.

With the above-mentioned structure, owing to the provision of theinsertion groove 15 with the broad portion 16 having its inside width W2larger than the inside width W1 of the insertion hole 14, when brazingthe insertion hole 14 of the plate 10 to the tube 3 inserted thereinto,the molten brazing filler metal R stays in the broad portion 16 of theinsertion groove 15 to form a fillet 17, so that it is possible toprevent the brazing filler metal R from reaching the tip surface of thetube 3. In other words, it is possible to prevent an opening at the tipof the tube 3 from being clogged up with the brazing filler metal R.

Again, since the broad portion 16 is formed throughout the insertiongroove 15 in this embodiment, there is produced a dimensional roombetween the tube 3 and the insertion groove 15 in engaging the end 3 aof the tube 3 in the insertion groove 15 via the insertion hole 14. Thatis, since the assembling of the plate 10 with the block 11 does notrequire to form these elements (i.e. the grooves 15, the tubes 3, etc.)with high dimensional accuracy, it is possible to attain an improvementin productivity and a reduction in manufacturing cost.

2^(nd). Embodiment

FIGS. 4 and 5 show the second embodiment of the present invention. Inthe second embodiment, elements identical to those of the firstembodiment are indicated with the same reference numerals respectivelyand their overlapping descriptions are eliminated. In those figures,FIG. 4 is an enlarged cross-sectional view of a substantial part of theheader tank, while FIG. 5 is an enlarged longitudinal sectional view ofthe substantial part of the header tank.

According to the second embodiment of the invention, the broad portion16 of the block 11 is formed at a bottom part 15 b of the insertiongroove 15.

An inlet portion 15 c of the insertion groove 15 is formed so that aninside width W3 is generally equal to the inside width W1 of theinsertion hole 14 of the plate 10.

Thus, according to the second embodiment of the invention, since the end3 a of the tube 3 is positioned in the broad portion 16, it is possibleto prevent the brazing filler metal R from reaching an opening at thetip of the tube 3, as similar to the first embodiment of the invention.Particularly, since it is possible to make the inside width W3 at theinlet portion 1 c of the insertion groove 15 generally equal to theinside W1 of the insertion hole 15 of the plate 10, the brazing fillermetal R molten in brazing reaches the inlet portion 15 c of theinsertion groove 15. Consequently, it is possible to fix the end 3 a ofthe tube 3 with both of the insertion hole 14 and the inlet portion 15 cof the insertion groove 15, whereby the joint strength of the tube 3with the header tank 2 can be enhanced.

1^(st). Modification of 2^(nd). Embodiment

FIG. 6 shows the first modification of the second embodiment. In thefirst modification, elements identical to those of the second embodimentare indicated with the same reference numerals respectively and theiroverlapping descriptions are eliminated. FIG. 6 is an enlargedlongitudinal sectional view of the substantial part of the header tank.

According to the modification, the block 11 is provided, at an inlet ofeach insertion groove 15, with chamfers 15 d, 15 d. Therefore, owing tothe provision of the chamfers 15 d, 15 d, it is possible to facilitatean insertion of the tube 3 into the insertion groove 15 in spite of thearrangement of the second embodiment where the inside width W3 of theinlet portion 15 c of the insertion groove 15 is generally equal to theinside width W1 of the insertion hole 14.

In a further modification, the “straight” chamfers 15 d, 15 d of eachinsertion groove 15 may be replaced by arc surfaces (not shown).

3^(rd). Embodiment

FIG. 7 shows the third embodiment of the invention. In the thirdembodiment, elements identical to those of the previously-mentionedembodiments are indicated with the same reference numerals respectivelyand their overlapping descriptions are eliminated. FIG. 7 is an enlargedlongitudinal sectional view of the substantial part of the header tank.

According to the third embodiment, as shown in FIG. 7, the insertiongroove 15 is provided, on the bottom surface 15 a, with a clearanceforming mechanism 18 configured to assure a clearance between the tipsurface 3 b of the tube 3 and the bottom surface 15 a.

In detail, the clearance forming mechanism 18 comprises a slantedsurface 18 a allowing the bottom surface 15 a to be inclined to the tipsurface 3 b of the tube 3.

It is noted in this embodiment that the slanted surface 18 a is inclinedwith respect to the bottom surface 15 a of the insertion groove 15.

In assembling the tubes 3 to the header tanks 2, according to the thirdembodiment, even if the tip surface 3 b of the tube 3 abuts on thebottom surface 15 a of the insertion groove 15 in the process ofengaging the tube 3 with the insertion groove 15 of the block 11 via theinsertion hole 14 of the plate 10, it is possible to prevent an openingat the tip of the tube 3 from being blocked up by the bottom surface 15a of the insertion groove 15 due to the formation of the slanted surface18 a (the bottom surface 15 a).

In other words, since the above-mentioned arrangement of this embodimentallows the tube 3 to be brazed to the header tank 2 under condition thatthe tip surface 3 b of the tube 3 is abutting on the bottom surface 15 aof the insertion groove 15, it is possible to improve the assemblingworkability.

1^(st). Modification of 3^(rd). Embodiment

FIG. 8 shows the first modification of the third embodiment. In thefirst modification, elements identical to those of the third embodimentare indicated with the same reference numerals respectively and theiroverlapping descriptions are eliminated. FIG. 8 is an enlargedlongitudinal sectional view of the substantial part of the header tank

In this modification, as shown in FIG. 8, the above slanted surface 18 aat the bottom surface 15 a of the insertion groove 15 is shaped to havea substantially V-shaped section on a bottom's center position Popposing the tip surface 3 b of the tube 3.

Since the tip surface 3 b of the tube 3 abuts on the V-shaped slantedsurface 18 a, the operation and effects of this modification are similarto those of the third embodiment mentioned above. Additionally, owing tothe abutment of tube's corners (edges) on both sides of the tip surface3 b with the slanted surface 18 a, the assembling of the tube 3 can bestabilized.

Alternatively, a valley bottom of the slanted surface 18 a may befurther formed so as to be either flat or arc, providing a trapezoidalsection.

2^(nd). Modification of 3^(rd). Embodiment

FIG. 9 shows the second modification of the third embodiment. In thesecond modification, elements identical to those of the third embodimentare indicated with the same reference numerals respectively and theiroverlapping descriptions are eliminated. FIG. 9 is an enlargedlongitudinal sectional view of the substantial part of the header tank.

In this modification, as shown in FIG. 9, the above slanted surface 18 aat the bottom surface 15 a of the insertion groove 15 has an arc-shapedsection.

Since the tip surface 3 b of the tube 3 abuts on the arc-shaped slantedsurface 18 a, the operation and effects of this modification are similarto those of the third embodiment mentioned above. As similar to thefirst modification, owing to the abutment of tube's corners (edges) onboth sides of the tip surface 3 a with the arc-shaped surface 15 a, theassembling of the tube 3 can be stabilized.

3^(rd). Modification of 3^(rd). Embodiment

FIG. 10 shows the third modification of the third embodiment. In thethird modification, elements identical to those of the third embodimentare indicated with the same reference numerals respectively and theiroverlapping descriptions are eliminated. FIG. 10 is an enlargedlongitudinal sectional view of the substantial part of the header tank.

According to this modification, the above clearance forming mechanism 18is formed by a recess 18 b on the bottom surface 15 a of the insertiongroove 15. The recess 18 b is also arranged at a bottom's positionopposing the tip surface 3 b of the tube 3.

Also noted that the recess 18 b is formed to penetrate the boundary wall11 a (FIG. 2) thereby communicating the cylindrical portions 12, 12(FIG. 2) with each other. Of course, the width of the recess 18 b isestablished smaller than a width of the so-flattened tube 3 in theshort-axis direction, thereby preventing the leading end of the tube 3from entering the recess 18 b.

According to the third modification, owing to the provision of therecess 18 b, it is possible to prevent the tip surface 3 b of the tube 3from being blocked up by the bottom surface 15 a of the insertion groove15 although the tube 3 abuts on the bottom surface 15 a of the insertiongroove 15.

Finally, it will be understood by those skilled in the art that theforegoing descriptions are nothing but three embodiments of thedisclosed heat exchanger and therefore, various changes andmodifications may be made within the scope of claims.

1. A heat exchanger comprising: a pair of header tanks arranged at apredetermined interval, each of the header tanks including an innermember having at least one insertion groove formed therein and an outermember having at least one insertion hole formed therein and coveringthe inner member thereby defining a hollow part in the header tank; anda plurality of tubes arranged between the header tanks in communicationwith the header tanks, each of the tubes having an end to be insertedinto the insertion hole of the outer member of the header tank and alsoinserted into the insertion groove of the inner member of the headertank, wherein the insertion groove has a broad portion of which insidewidth is larger than an inside width of the insertion hole, wherein thetube is brazed to the outer member's part about the insertion hole. 2.The heat exchanger of claim 1, wherein the broad portion is formed overthe insertion groove.
 3. The heat exchanger of claim 1, wherein thebroad portion is formed at the bottom of the insertion groove.
 4. Theheat exchanger of claim 1, wherein the insertion groove is provided, ata bottom surface thereof, with a clearance forming mechanism configuredto form a clearance between a tip surface of the tube and the bottomsurface of the insertion groove.
 5. The heat exchanger of claim 4,wherein the clearance forming mechanism comprises the bottom surface ofthe insertion groove, which is inclined to the tip surface of the tube.6. The heat exchanger of claim 5, wherein the bottom surface inclined tothe tip surface of the tube composes an arc-shaped section.
 7. The heatexchanger of claim 4, wherein the clearance forming mechanism comprisesa recess formed on the bottom surface of the insertion groove, at aposition opposing to the tip surface of the tube.